By using operant conditioning procedures of proven utility in behavioral pharmacology, the proposed research will attempt to increase the "resolving power" of these methods by concurrently measuring peak force, duration, and interresponse time of individual responses. These dependent variables will be used to study the effects of selected neuroleptics (antipsychotic, antischizophrenic) drugs upon behavior maintained by simple schedules of reinforcement, and by additional methods which will permit measurement of discriminative motor control in rats. More specifically, the motor features of operant responses will be used to characterize the varying degrees of extrapyramidal effects (which in man are regarded as side-effects) produced by antischizophrenic drugs such as haloperidol and clozapine. Many of the motor effects observed consequent to the use of major tranquilizers develop after chronic use. Therefore, in addition to assessing acute drug effects, some of the proposed experiments include evaluation of selected neuroleptics over several weeks, with continued monitoring of specific motor features of behavior for weeks after discontinuing drug treatment. These experiments should contribute to the evolution of behavioral procedures that permit effective classification of antipsychotic drugs according to their degrees of extrapyramidal side effects. Moreover, such techniques should be of particular value in detecting side effect liabilities of new compounds during pre-clinical testing.